Cooling System With Dual Reversing Fans

ABSTRACT

A cooling system comprises a first cooling package, a second cooling package, and a fan control system. The first cooling package comprises a first fan and at least one heat exchanger to cool at least one fluid associated with the machine. The first fan is configured to rotate in a cooling direction and an opposite cleaning direction. The second cooling package comprises a second fan and at least one heat exchanger to cool at least one fluid associated with the machine. The second fan is configured to rotate in a cooling direction and an opposite cleaning direction. The fan control system is configured to alternate the first and second fans between a first cleaning mode and a second cleaning mode.

FIELD OF THE DISCLOSURE

The present disclosure relates to a cooling system for cooling one ormore fluids of a machine.

BACKGROUND OF THE DISCLOSURE

Exhaust emissions standards are becoming more stringent. Such standardshave placed an increased heat-rejection demand on cooling systems ofoff-highway equipment.

Vehicles use a cooling system to cool the engine, retarder,transmission, brakes, and air-conditioner condenser. The coolers of thecooling system get dirty over a period of use and, in at least somecases, receive manual cleaning by blowing them with an air gun. Thismaintenance process takes time and gets more difficult to perform if thedirt is left to accrue. It also adds to the time that the vehicle isunproductive. If left unattended, the vehicle will start to overheat andlose performance and eventually could fail one of the major components.

SUMMARY OF THE DISCLOSURE

According to the present disclosure, a cooling system comprises a firstcooling package, a second cooling package, and a fan control system. Thefirst cooling package comprises a first fan and at least one heatexchanger to cool at least one fluid associated with the machine. Thefirst fan is configured to rotate in a cooling direction and an oppositecleaning direction. The second cooling package comprises a second fanand at least one heat exchanger to cool at least one fluid associatedwith the machine. The second fan is configured to rotate in a coolingdirection and an opposite cleaning direction. The fan control system isconfigured to alternate the first and second fans between a firstcleaning mode and a second cleaning mode.

In the first cleaning mode, the first and second fans concurrentlyrotate respectively in their cleaning and cooling directions advancingair in a first flow direction from the first fan to the second fan pastthe at least one heat exchanger of each of the first and second coolingpackages. In the second cleaning mode the first and second fansconcurrently rotate respectively in their cooling and cleaningdirections advancing air in a second flow direction opposite the firstflow direction from the second fan to the first fan past the at leastone heat exchanger of each of the first and second cooling packages.

In an embodiment, the fan control system is configured to alternatesuccessively the first and second fans between the first cleaning modeand the second cleaning mode during an exchanger-cleaning event.Successive alternation between the first and second cleaning modespromotes cleaning of the heat exchangers of foreign material (dirt,debris, etc.).

In another embodiment, during an exchanger-cleaning event, the fancontrol system is configured to operate the first and second fanssequentially in the first cleaning mode, an interim cleaning mode, andthe second cleaning mode. In the interim cleaning mode, the first andsecond fans concurrently rotate respectively in their cleaningdirections, promoting removal of debris from the compartment in whichthe heat exchangers are positioned.

In yet another embodiment, the fan control system is configured toalternate successive exchanger-cleaning events between the firstcleaning mode and the second cleaning mode, with an exchanger-coolingevent in a cooling mode therebetween. Such operation promotes fuelefficiency.

The above and other features will become apparent from the followingdescription and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description of the drawing refers to the accompanyingfigures in which:

FIG. 1 is a simplified top view showing advancement of air by a pair offans during a cooling mode in which the fans operate in their cooling orforward directions;

FIG. 2 is a simplified top view showing advancement of air during afirst cleaning mode in which the first fan (e.g., left side of drawing)operates in its cleaning or reverse direction as the “reverse fan” andthe second fan (e.g., right side of drawing) operates in its cooling orforward direction as the “forward fan”;

FIG. 3 is a simplified top view showing advancement of air during asecond cleaning mode in which the first fan operates in its cooling orforward direction as the forward fan and the second fan operates in itscleaning or reverse direction as the reverse fan;

FIG. 4 is a simplified top view showing advancement of air during aninterim mode in which each of the first and second fans operates in itscleaning or reverse direction as a reverse fan;

FIG. 5 is a simplified schematic view of a fan control system;

FIG. 6 is a first control routine that cycles the fans between the firstand second cleaning modes during an exchanger-cleaning event;

FIG. 7 is an alternative embodiment of the first control routine addingan interim step in which both fans are reversed simultaneously betweenthe first and second cleaning modes to promote debris removal;

FIG. 8 is a second control routine in which successiveexchanger-cleaning events alternate between the first and secondcleaning modes, with an exchanger-cooling event in a cooling modetherebetween; and

FIG. 9 is a chart showing sequential reversal of the fans in anexchanger-cleaning event.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, there is shown a machine 10 which may take the formof, for example, an articulated dump truck or other work vehicle havinga fore-aft axis 11. Exemplarily, as an articulated dump truck, themachine 10 has a front section 12 and a rear section, the front and rearsections being articulated to one another and positioned along thefore-aft axis 11. The front section 12 has the operator's station and anengine compartment 18 in front of the operator's station. The rearsection has a tippable dump body configured to carry a payload.

The machine 10 has a cooling system 22 for cooling a number of fluids ofthe machine 10. The cooling system 22 has a first cooling package 24, asecond cooling package 26, and a fan control system 28.

The first cooling package 24 has a first fan 30 and at least one heatexchanger 32 to cool at least one fluid associated with the machine 10.The first fan 30 is configured to rotate in a cooling or forwarddirection 34-1 and an opposite cleaning or reverse direction 34-2.

The second cooling package 26 has a second fan 36 and at least one heatexchanger 38 to cool at least one fluid associated with the machine 10.The second fan 36 is configured to rotate in a cooling or forwarddirection 40-1 and an opposite cleaning or reverse direction 40-2.

The fan control system 28 is configured to operate the first and secondfans 30, 36 in a cooling mode to cool one or more fluids of the machine10 during an exchanger-cooling event and in one or more cleaning modesto clean the at least one heat exchanger 32, 38 of each of the first andsecond cooling packages 24, 26 during an exchanger-cleaning event.Referring to FIG. 1, in the cooling mode, the first and second fans 30,36 concurrently rotate respectively in their cooling directions 34-1,40-1 advancing air from a common air inlet respectively past the firstand second cooling packages 24, 26 to the first and second fans 30, 36and out respective air outlets.

The fan control system 28 is configured to alternate successively thefirst and second fans 30, 36 between a first cleaning mode and a secondcleaning mode during an exchanger-cleaning event. Referring to FIG. 2,in the first cleaning mode the first and second fans 30, 36 concurrentlyrotate respectively in their cleaning and cooling directions 34-2, 40-1advancing air in a first flow direction 42 from the first fan 30 to thesecond fan 36 past the at least one heat exchanger 32, 38 of each of thefirst and second cooling packages 24, 26. Referring to FIG. 3, in thesecond cleaning mode the first and second fans 30, 36 concurrentlyrotate respectively in their cooling and cleaning directions 34-1, 40-2advancing air in a second flow direction 44 opposite the first flowdirection 42 from the second fan 36 to the first fan 30 past the atleast one heat exchanger 32, 38 of each of the first and second coolingpackages 24, 26.

The fan control system 28 is configured to cycle the first and secondfans 30, 36 between the first and second cleaning modes for one or morecycles during the exchanger-cleaning event. For example, the fan controlsystem 28 is configured to cycle the fans 30, 36 between the first andsecond cleaning modes for one cycle during the exchanger-cleaning event.

Exemplarily, the first and second cooling packages 24, 26 are positionedon laterally opposite sides of a fore-aft axis 11 of the machine 10 suchthat the first and second flow directions 42, 44 are laterally oppositeto one another. The first cooling package 24 may be positioned on theright-hand side of the axis 11, and the second cooling package 26 may bepositioned on the left-hand side of the axis 11. The at least one heatexchanger 32 of the first cooling package 24 and the at least one heatexchanger 38 of the second cooling package 26 are positioned laterallybetween the first and second fans 30, 36. Exemplarily, an internalcombustion engine 48 (e.g., diesel engine) is positioned laterallybetween the first and second cooling packages 24, 26.

Each of the first and second cooling packages 24, 26 may have a numberof heat exchangers. Exemplarily, the first cooling package 24 has threeunits of one or more heat exchangers 32 stacked laterally relative toone another, with a laterally outward unit, a laterally inward unit, anda laterally intermediate unit positioned laterally between the laterallyoutward and inward units. The laterally outward unit is positionedlaterally between the first fan 30 and the laterally intermediate unit.The laterally inward unit is positioned laterally between the laterallyintermediate unit and the engine 48. The laterally outward unit is aradiator 32-1 configured to cool engine coolant. The laterallyintermediate unit is a combination cooler having, from rear to front, atransmission-and-retarder oil cooler 32-2 configured to cool oil of thetransmission and retarder and a hydraulic oil cooler 32-3 configured tocool hydraulic oil. The transmission-and-retarder oil cooler and thehydraulic oil cooler are adjacent to one another and are fastened toanother (e.g., using bolts and nuts). The laterally inward unit is afuel cooler 32-4 configured to cool fuel. The first cooling package 24may be configured in any suitable fashion (e.g., the number, size, use,layout, etc. of heat exchangers may be different for a given machine).

Exemplarily, the second cooling package 26 has two units of one or moreheat exchangers 38 stacked laterally relative to one another, with alaterally outward unit, a laterally inward unit, and a laterallyintermediate unit positioned laterally between the laterally outward andinward units. The laterally outward unit is positioned laterally betweenthe second fan 36 and the laterally intermediate unit. The laterallyinward unit is positioned laterally between the laterally outward unitand the engine 48. The laterally outward unit is a radiator 38-1configured to cool engine coolant. The laterally intermediate unit is acombination cooler having, from rear to front, a first brake cooler 38-2configured to cool an axle and associated brakes (e.g., the middle axleof an articulated dump truck, a second brake cooler 38-3 configured tocool an axle and associated brakes (e.g., the front axle of anarticulated dump truck), and a charge-air cooler 38-4 configured to coolpressurized engine intake air. The second brake cooler is positionedbetween the first brake cooler and the air conditioner condenser and isfastened to them (e.g., using bolts and nuts). The laterally inward unitis an air-conditioning condenser 38-5. The second cooling package 26 maybe configured in any suitable fashion (e.g., the number, size, use,layout, etc. of heat exchangers may be different for a given machine).

Exemplarily, the two radiators 32-1, 38-1 of the first and secondcooling packages 24, 26 are flow-parallel to one another. In such acase, a first node is coupled fluidly to a coolant outlet of the engine48 and respective coolant inlets of the two radiators, and a second nodeis coupled fluidly to respective coolant outlets of the two radiatorsand a coolant inlet of the engine 48.

Referring to FIG. 5, the fan control system 28 may be configured in anysuitable manner to control operation of the fans 30, 36. Exemplarily,the fan control system 28 has a first electro-hydraulic system 68 forthe first fan 30 and a second electro-hydraulic system 69 for the secondfan 36, the systems 68, 69 sharing a hydraulic fluid reservoir tank.Each electro-hydraulic system 68, 69 has a variable displacementhydraulic pump 70 and a hydraulic motor 72. The motor 72 is coupledmechanically to the respective fan 30, 36 to drive that fan in eitherdirection. The pump 70 is coupled hydraulically to the respective motor72 to drive that motor 72, and may be, for example, an axial-pistonpump. The first electro-hydraulic system 68 has a displacement controlmechanism that provides pressure-compensated, load-sense (LS) control ofthe pump 70 (e.g., of the swash plate of the pump 70). The displacementof the pump 70 of the second electro-hydraulic system 69 iselectronically controlled using a displacement control mechanismdiscussed below. The controller 58 is coupled electrically to a speedsensor (e.g., Hall-effect sensor with 12 pulses per revolution) in eachmotor 72 to receive information indicative of the rotational speed ofthe respective fan 30, 36 in order to control such speed.

Each electro-hydraulic system 68, 69 has a directional control valve 74,a reverse valve 76, and a speed valve 78. The directional control valve74 is configured to direct hydraulic fluid selectively to either of twowork ports of the motor 72 to control the direction of rotation of themotor 72. The reverse valve 76 is configured as an on/off valve and iscoupled electrically to an electric first controller 58 of the machine10 (e.g., chassis control unit) so as to be under the control of thecontroller 58. The reverse valve 76 is coupled hydraulically to the pump70 and a pilot port of the directional control valve 74 to direct supplypressure to the pilot port of the directional control valve 74 when thesolenoid of the reverse valve 76 is energized by the controller 58.Energizing and de-energizing the reverse valve 74 causes the spool ofthe directional control valve 74 to shift accordingly to change thedirection of flow to the motor 72 and thus the direction of rotation ofthe respective fan 30, 36.

An intermediate, transition section of the directional control valve 74is configured to couple fluidly the two work ports of the motor 72through the valve 74 momentarily allowing the respective fan 30, 36 tofreewheel during shifting of the spool between a first positiondirecting hydraulic fluid to a first work port of the motor 72 and asecond position directing hydraulic fluid to a second work port of themotor 72. Such a work port connection promotes motor life by avoiding asudden deadhead of the motor 72 that might otherwise occur in theabsence of the transition section.

Each electro-hydraulic system 68, 69 has a first pressure-relief valve77 and a second pressure-relief valve 79. The first pressure-reliefvalve 77 is coupled fluidly to the pressure supply line from therespective pump 52 and a return line to tank. The second pressure-reliefvalve 79 is coupled fluidly to either side of the first pressure-reliefvalve 77 in parallel thereto, and has a pressure-relief setting lowerthan that of the valve 77. The second pressure-relief valve 77 iscoupled electrically to the first controller 58 so as to be under thecontrol of that controller 58. When the controller 58 energizes thesolenoid of the reverse valve 76, it energizes the solenoid of thesecond pressure-relief valve 79 momentarily so as to relieve pressure inthe pressure supply line as the spool of the directional control valve74 passes through its intermediate, transition section, avoidingtransmission of a pressure spike to upstream components with respect tothe first electro-hydraulic system 68 and to the pump 70 with respect tothe second electro-hydraulic system 69.

The speed valve 78 of the first electro-hydraulic system 68 isconfigured, for example, as a proportional load-sense relief valve andis operable to vary the speed of rotation of the fan 30. The speed valve78 is coupled electrically to the controller 58 so as to be under thecontrol of the controller 58 (e.g., by pulse-width modulation or “PWM”such as, for example, PWM to ground with system voltage to high side ofvalve 78 in response to vehicle start-up). The controller 58 isconfigured to command the speed valve 78 to open by energizing itssolenoid in order to bleed hydraulic fluid from an associated load senseline LS1 so as to slow the fan speed. De-energizing the solenoid of thespeed valve 78 increases the fan speed.

The speed valve 78 of the second electro-hydraulic system 69 isconfigured, for example, as a proportional valve and is included in thedisplacement control mechanism for the pump 70 of the system 69. Thedisplacement control mechanism has a hydraulic first cylinder 86 and ahydraulic second cylinder 88, both cylinders 86, 88 coupled to thedisplacement control of the pump 70 (e.g., swash plate). The speed valve78 has two work ports coupled fluidly respectively to the first cylinder86 and the second cylinder 88. The speed valve 78 is spring-biased toroute hydraulic fluid from the supply line to the first cylinder 86 soas to displace the pump 70 fully for maximum speed of the second fan 36.The speed valve 78 is coupled electrically to the controller 58 so as tobe under the control of the controller 58 (e.g., by pulse-widthmodulation or “PWM” such as, for example, PWM to ground with systemvoltage to high side of valve 78 in response to vehicle start-up). Thecontroller 58 is configured to command the speed valve 78 to shift byenergizing its solenoid in order to route hydraulic fluid from thesupply line to the second cylinder 88 so as to slow the second fan 36.De-energizing the solenoid of the speed valve 78 increases the fanspeed.

Each pump 70 can be a pump dedicated to the respective fan 30, 36, or itmay be shared with other functions. Exemplarily, the pump 70 of thesecond electro-hydraulic system 69 is dedicated to the second fan 36,whereas the pump 70 of the first electro-hydraulic system 68 is sharedwith other functions (e.g., steering, brake, axle cooling, dump bodytip, suspension) and, as such, may be the main hydraulic pump of themachine 10. In such a case, the pump 70 of the first electro-hydraulicsystem 68 may be driven off of the transmission, coupled to the engine48, and the pump 70 of the second electro-hydraulic system 69 may bedriven off the engine 48 (e.g., mounted directly to the engine 48) witha gear pump exemplarily stacked behind it.

For simplification, with respect to the first electro-hydraulic system68, components between the “shared” pump 70 and the motor 72 associatedwith the fan 30 are shown, although the other functions are not shown.Such components include an attenuator 80, a priority valve 81, anelectro-hydraulic cut-off valve 82, and a compensator valve 84. Theattenuator 80 attenuates noise due, for example, to pressure pulsationfrom the pump 70 of the first electro-hydraulic system 68. The priorityvalve 81 establishes priority flow for steering (and also for brakes butmainly for steering). The cut-off valve 82 is closed during tipping ofthe dump body of the machine 10 to decrease the time that it takes totip the dump body in response to a signal from the first controller 58due to movement of the dump body (e.g., caused by displacement of thedump lever or actuation of a dump body-up button or a dump body-downbutton). The compensator valve 84 regulates the pressure supplied to themotor 72 to be that which is commanded of the speed valve 78 (e.g., ifthe load-sense system causes the pump 70 to output a pressure greaterthan what is needed for the fan 30, the compensator valve 84 will reducethat pressure to the pressure called for by the speed valve 78). Theload-sense system for the “shared” pump 70 is identified as “LS1” inFIG. 5, and exemplarily includes a network of shuttle valves associatedwith various functions to establish the load-sense signal back to thepump control. A system pressure-relief unit 89 is positioned in thesystem 68 ahead of the function(s) of the system 68.

Referring to FIG. 6, there is shown a flowchart of a control routine 110for cleaning the heat exchangers 32, 38 of the first and second coolingpackages 24, 26 in the cleaning mode. The cleaning mode may be initiatedautomatically or manually by the operator. Automatic initiation occursin step 112, and manual initiation occurs in step 114.

In step 112, the electric first controller 58 of the control system 28(e.g., the chassis control unit) monitors elapsed time (t) since the endof the last cleaning event of the cooling packages 24, 26, anddetermines if a predetermined period of time (Δt) has elapsed since theend of that event. A timer 62 tracks such elapsed time, and is includedin the controller 58, or may be a stand-alone device or part of anothercontroller. The predetermined period of time may be selected by theoperator through, for example, a display monitor at the operator'sstation (e.g., ½ hour, 1 hour, 2 hours, 3 hours, 4 hours), or it may bea default value (e.g., 4 hours). If the predetermined period of time haselapsed, the routine 110 advances to step 116. If no, the controller 58continues to monitor elapsed time since the last exchanger-cleaningevent.

In step 114, an operator or other person can manually request activationof the cleaning mode through a display monitor at the operator'sstation. If a manual request has been received, the routine 110 advancesto step 116.

In step 116, the controller 58 determines whether any of a number ofinhibit conditions is present. The conditions monitored may include, forexample: the temperature of any of the fluids in the heat exchangers ofthe cooling packages 24, 26 is at or above its respective maximumallowable temperature (since a cleaning event will reduce cooling); thewindshield wipers are off (since wiper activation is indicative of rainwhich could cause a cloud of dust discharged from the machine 10 duringcleaning to stick to windows of the operator's station); and a dieselparticulate filter is being regenerated (e.g., based on a CAN messagereceived by the controller 58 from an electric second controller 60 suchas an engine control unit). The controller 58 receives inputs indicativeof whether any such inhibit condition exists. If the controller 58determines that an inhibit condition exists, the controller 58 waits toactivate the cleaning mode until such condition terminates. If a manualrequest for cleaning was received, the controller 58 may initiateactivation of an alert (e.g., on the display monitor) indicating thatthe cleaning mode is inhibited. If no inhibit condition exists, theroutine 110 advances to step 118.

Other inhibit conditions may include, for example, one or more of thefollowing: engine speed is not greater than a threshold engine speed(e.g., 1400 rpm), since lower engine speeds may not provide sufficienthydraulic flow to reach maximum fan speed (in other words, engine speedsgreater than 1400 rpm may provide sufficient hydraulic flow to reachmaximum fan speed; it is thought that engine idle speed may even besufficient); and ground speed of the machine 10 is greater than athreshold ground speed (e.g., 5 miles per hour), so as to reduce thelikelihood that a person is in the path of discharge.

In step 118, the controller 58 activates an exchanger-cleaning event inwhich the controller 58 alternates successively the first and secondfans 30, 36 between the first cleaning mode and the second cleaningmode. Such alternating succession may occur for one or more cycles(e.g., one cycle). During each cycle, the first cleaning mode isperformed followed by performance of the second cleaning mode.

In step 118-1 of step 118, the controller 58 activates the firstcleaning mode. In the first cleaning mode, the first and second fans 30,36 concurrently rotate respectively in their cleaning and coolingdirections 34-2, 40-1 advancing air in a first flow direction 42laterally relative to the fore-aft axis 11 from the first fan 30 to thesecond fan 36 past the at least one heat exchanger 32, 38 of each of thefirst and second cooling packages 24, 26.

Referring to FIG. 9, to reverse the first fan 30 from its coolingdirection to its cleaning direction, in time T1, the controller 58commands operation of the speed valve 78 associated with the first fan30 (gradually energizes its solenoid) (i.e., the first speed valve 78)to ramp down the speed of the first fan 30 at a predetermined rate(e.g., 100 rpm/second) toward a zero fan speed using the speedinformation from the speed sensor in the first fan motor 72. Suchramping down helps to avoid fan motor cavitation. When the fan speedreaches a predetermined fan idle speed (e.g., 600 rpm), the controller58 commands operation of the first speed valve 78 so as to command thefirst fan 30 to the zero fan speed (i.e., commands maximum current tothe valve 78 assuming no fault requiring abort), and begins to monitorthe fan speed for up to a predetermined period of time (e.g., 10seconds) using the speed information from the speed sensor in the firstfan motor 72 (the controller 58 is unable to control the 100 rpm/secondrate below the fan idle speed). The solenoid of the reverse valve 76associated with the first fan 30 9 (i.e., the first reverse valve 76) isde-energized during time T1.

If, during the predetermined period of time, the fan speed reaches zero,time T2 starts immediately. If, at the end of the predetermined periodof time, the fan speed does not reach zero but reaches below a low-speedthreshold (e.g., 100 rpm), time T2 starts at the end of thepredetermined period of time. If neither condition occurs, thecontroller 58 aborts reversal of the first fan 30, and begins reversalof the second fan 36 (i.e., advances the second fan 36 from T1-T7). Asfor the first fan 30, the controller 58 commands operation of the firstspeed valve 78 (gradually decreases its current) to ramp up the speed ofthe first fan 30 at a predetermined rate (e.g., 100 rpm/second) to avariable forward speed based on the cooling need of the first coolingpackage 24 using the speed information from the speed sensor in thefirst fan motor 72.

In time T2, the controller 58 commands operation of the first speedvalve 78 so as to command the first fan 30 to the zero fan speed (i.e.,commands maximum current to the valve 78 assuming no fault requiringabort), and monitors the fan speed of the first fan 30 for apredetermined period of time using the speed information from the speedsensor in the first fan motor 72 to confirm if the fan speed remainsbelow the low-speed threshold. The predetermined period of time may bebetween a few milliseconds and a few seconds. It may be, for example, 10milliseconds or, preferably, two seconds to ensure that the fan speedhas indeed reduced to a desired level for changing its direction ofrotation since the speed sensor does not indicate direction of rotation.If, during the predetermined period of time, the fan speed of the firstfan 30 is equal to or greater than the low-speed threshold, thecontroller 58 aborts reversal of the first fan 30 and begins reversal ofthe second fan 36 (i.e., advances the second fan 36 from T1-T7), and,regarding the first fan 30, the controller 58 commands operation of thefirst speed valve 78 (gradually decreases its current) to ramp up thespeed of the first fan 30 at a predetermined rate (e.g., 100 rpm/second)to a variable forward speed based on the cooling need of the firstcooling package 24 using the speed information from the speed sensor inthe first fan motor 72. The solenoid of the first reverse valve 76 isde-energized during time T2.

In time T3, the controller 58 energizes the solenoid of the firstreverse valve 76 and commands operation of the first speed valve 78(proportionally energizes its solenoid) so as to reverse the directionof hydraulic flow to the first fan motor 72 and command the speed of thefirst fan 30 to a predetermined reverse speed threshold (e.g., 1600rpm). The controller 58 monitors the speed information from the speedsensor in the first fan motor 72 for up to a predetermined amount oftime (e.g., two seconds) to confirm if a non-zero fan speed has beenachieved, as there will be a natural initial system delay (due, forexample, to solenoid saturation, valve hysteresis, and time to measurefan speed). If the non-zero fan speed has not been achieved within thepredetermined period of time, the controller 58 aborts reversal of thefirst fan 30 and begins reversal of the second fan 36 (i.e., advancesthe second fan 36 from T1-T7). During abort of the first fan 30, thecontroller 58 de-energizes the solenoid of the first reverse valve 76and commands operation of the first speed valve 78 (gradually decreasesits current) to ramp up the speed of the first fan 30 at a predeterminedrate (e.g., 100 rpm/second) to a variable forward speed based on thecooling need of the first cooling package 24 using the speed informationfrom the speed sensor in the first fan motor 72.

Time T4 begins when the controller 58 determines that the first fan 30has achieved a non-zero fan speed using the speed information from thespeed sensor in the first fan motor 72. In time T4, the controller 58continues to energize the solenoid of the first reverse valve 76 and toenergize proportionally the solenoid of the first speed valve 78 so asto command the predetermined reverse speed threshold, and monitors thefan speed for up to a predetermined period of time (e.g., four seconds)to confirm if the predetermined reverse speed threshold has beenachieved. If the predetermined reverse speed threshold has not beenachieved in the predetermined period of time, the controller 58 abortsreversal of the first fan 30, and begins reversal of the second fan 36(i.e., advances the second fan 36 from T1-T7).

To abort reversal of the first fan 30 in time T4, the controller 58commands operation of the first speed valve 78 so as to command thefirst fan 30 to a zero fan speed (i.e., commands maximum current to thevalve 78 assuming no fault requiring machine shutdown and restart so asto de-energize the valve 78 thereby resetting it in case the secondspeed valve 78 is malfunctioning) and monitors the fan speed for up to apredetermined period of time (e.g., 10 seconds) using the speedinformation from the speed sensor in the first fan motor 72. If, duringthe predetermined period of time, the fan speed reaches zero, or, at theend of the predetermined period of time, the fan speed is at least belowthe low-speed threshold, the controller 58 continues to command the zerofan speed for another predetermined period of time (e.g., two seconds),in response to elapse of which the controller 58 de-energizes thesolenoid of the first reverse valve 76 and commands operation of thefirst speed valve 78 (gradually decreases its current) to ramp up thespeed of the first fan 30 at a predetermined rate (e.g., 100 rpm/second)to a variable forward speed based on the cooling need of the firstcooling package 24 using the speed information from the speed sensor inthe first fan motor 72. The controller 58 begins reversal of the secondfan 36 when the speed of the first fan 30 drops below the low-speedthreshold (i.e., advances the second fan 36 from T1-T7).

When the predetermined reverse speed threshold is reached, time T5begins, in which the controller 58 continues to energize the solenoid ofthe first reverse valve 76 and to energize the solenoid of the firstspeed valve 78 so as to command the speed of the first fan 30 to be thereverse speed threshold for a predetermined period of reverse time. Thatpredetermined period of time may be, for example, 30 seconds, or, in thecase of worksites with excessive debris, 60 seconds. Such period of timemay be selectable by the operator via a display monitor in theoperator's station. Once the fan speed reaches the reverse speedthreshold, the controller 58 starts counting the amount of reverse timein which the first fan 30 is at or above the reverse speed threshold. Ifthe fan speed drops below the threshold, the controller 58 stopscounting the reverse time. Instead, the controller 58 starts countingthe amount of time below the threshold. As such, when the fan speed isat or above the threshold, time is accrued toward the predeterminedperiod of reverse time, whereas, when the fan speed is below thethreshold, time is accrued toward a predetermined period of fault timewhich may be, for example, 30 seconds. The reverse time and the faulttime are thus both cumulative. If the reverse time is reached before thefault time is reached, the controller 58 proceeds to time T6. If thefault time is reached before the reverse time is reached, the controller58 aborts reversal of the first fan 30, and begins reversal of thesecond fan 36. The abort sequence in time T5 is the same as the abortsequence in T4.

In time T6, the controller 58 commands operation of the first speedvalve 78 to command the speed of the first fan 30 to zero (i.e.,commands maximum current to the valve 78 assuming no fault requiringabort), at an uncontrolled rate. Since this speed decrease isuncontrolled (the first fan 30 freewheels), the controller 58 monitorsthe fan speed for up to a predetermined period of time (e.g., 10seconds) using the speed information from the speed sensor in the firstfan motor 72. If, during the predetermined period of time, the fan speedreaches zero, time T7 starts immediately. If, at the end of thepredetermined period of time, the fan speed does not reach zero butreaches below the low-speed threshold (e.g., 100 rpm), time T7 starts atthe end of the predetermined period of time. If neither conditionoccurs, the controller 58 aborts the exchanger-cleaning event altogetherin order to avoid reversing both fans 30, 36 at the same time, and maytherefore require the machine 10 to be shut down and re-started (e.g.,so as to de-energize the second speed valve 78 thereby resetting it incase the second speed valve 78 is malfunctioning).

In time T7, the controller 58 commands operation of the first speedvalve 78 so as to command the first fan 30 to the zero fan speed (i.e.,commands maximum current to the valve 78 assuming no fault requiringabort), and monitors the fan speed of the first fan 30 for apredetermined period of time using the speed information from the speedsensor in the first fan motor 72 to confirm if the fan speed remainsbelow the low-speed threshold. The predetermined amount of time may bebetween a few milliseconds and a few seconds. It may be, for example, 10milliseconds or, preferably, two seconds to ensure that the fan speedhas indeed reduced to a desired level for changing its direction ofrotation since the speed sensor does not indicate direction of rotation.If the fan speed remains below the low-speed threshold for thepredetermined period of time, at the end of T7, the controller 58de-energizes the solenoid of the first reverse valve 76 and commandsoperation of the first speed valve 78 (gradually decreases its current)to ramp up the speed of the first fan 30 at a predetermined rate (e.g.,100 rpm/second) to a variable forward speed based on the cooling need ofthe first cooling package 24 using the speed information from the speedsensor in the first fan motor 72. If the fan speed does not remain belowthe low-speed threshold, the controller 58 aborts the exchanger-cleaningevent altogether in order to avoid reversing both fans 30, 36 at thesame time, and may therefore require the machine 10 to be shut down andre-started (e.g., so as to de-energize the second speed valve 78 therebyresetting it in case the second speed valve 78 is malfunctioning).

The routine 110 advances to step 118-2 of step 118 as soon as the zerofan speed of the first fan 30 has been achieved in T6 or if the fanspeed of the first fan 30 is below the low-speed threshold at the end ofthe predetermined period of time of T6. In step 118-2, the controller 58activates the second cleaning mode, while concluding the first cleaningmode by advancing the first fan 30 through T7 and ramping its fan speedto a forward speed.

In the second cleaning mode, the first and second fans 30, 36concurrently rotate respectively in their cooling and cleaningdirections 34-1, 40-2 advancing air in a second flow direction 44opposite the first flow direction 42 laterally relative to the fore-aftaxis 11 from the second fan 36 to the first fan 30 past the at least oneheat exchanger 32, 38 of each of the first and second cooling packages24, 26. To do so, the controller 58 reverses the second fan 36 accordingto the reversal sequence (i.e., T1-T7) described above for the first fan30 in the first cleaning mode 118-1 and aborts in the same manner ifnecessary, except that, in the event of an abort of reversal of thesecond fan 36 in any of T1-T5, the controller 58 aborts theexchanger-cleaning event altogether (i.e., does not reverse the firstfan 30 since the first fan 30 would have already been reversed). Withrespect to the second cleaning mode, the speed valve 78 associated withthe second fan 36 (second speed valve 78) and the reverse valve 76associated with the second fan 36 (second reverse valve 76) areinvolved. In the event of an abort during T6 or T7, the controller 58aborts the exchanger-cleaning event altogether, and may thereforerequire the machine 10 to be shut down and re-started (e.g., so as tode-energize the second speed valve 78 thereby resetting it in case thesecond speed valve 78 is malfunctioning).

When finished with the reversal sequence for the second fan 36 (i.e.,T1-T7), the control routine 110 advances to step 120 so as to resume thecooling mode. In step 120, if the fan speed remains below the low-speedthreshold for the predetermined period of time, at the end of T7, thecontroller 58 de-energizes the second reverse valve 76 and commandsoperation of the second speed valve 78 (gradually decreases its current)to ramp up the speed of the second fan 36 at a predetermined rate (e.g.,100 rpm/second) to a variable forward speed based on the cooling need ofthe second cooling package 26 using the speed information from the speedsensor in the second fan motor 72. As alluded to above, if the fan speeddoes not remain below the low-speed threshold, the controller 58 abortsthe exchanger-cleaning event altogether, and may therefore require themachine 10 to be shut down and re-started (e.g., so as to de-energizethe second speed valve 78 thereby resetting it in case the second speedvalve 78 is malfunctioning).

During reversal of the first fan 30, the controller 58 commandsoperation of the second fan 36 at a forward speed based on the coolingneed of the cooling package 26 through de-energization of the secondreverse valve 76 and proportional control of the second speed valve 78.An electric second controller 60 (e.g., engine control unit coupledelectrically to the first controller 58 via a controller area network,i.e., CAN) determines the fan speed of the second fan 36 based on thecooling need of the fluid of the second cooling package 26 closest toits upper temperature limit (alternatively, the electric firstcontroller 58 could perform this function). Exemplarily, the secondcontroller 60 receives the engine coolant temperature from a temperaturesensor, and sends this value to the first controller 58 fordetermination of whether an inhibit condition exists. The secondcontroller 60 sends that fan speed to the electric first controller 58which controls the second speed valve 78 so as to operate the second fan36 at that fan speed. The first fan 30 is operated in a correspondingmanner during reversal of the second fan 36.

Referring to FIGS. 4 and 7, an alternative embodiment of the step 118 isshown as step 218, and includes an interim step 218-3 due to overlap ofactivation of the first and second cleaning modes in steps 218-1 and218-2, respectively. In step 218-3, the controller 58 commands operationof the fans 30, 36 such that the fans 30, 36 concurrently rotaterespectively in their cleaning directions for an interim predeterminedperiod of time so as to blow air inwardly toward the engine 48 to causedebris to blow out any openings in the compartment 18 (e.g., anyopenings between panels, and front grill).

To do so, in step 218-2, the controller 58 activates the first cleaningmode, advancing the first fan 30 in sequence from T1 to T5, while thesecond fan 36 continues to operate at a variable fan cooling speed.While the first fan 30 is still in T5 or immediately afterwards duringwhich the controller 58 keeps the first fan 30 at the predeterminedreverse speed threshold (e.g., 1600 rpm), the controller 58 activatesthe second cleaning mode reversing the second fan 36 from its coolingdirection to its cleaning direction by advancing it in sequence throughT1, T2, T3, and T4 to the predetermined reverse speed threshold. Thecontroller 58 keeps the fan speed of the fans 30, 36 at thepredetermined reverse speed threshold for an interim predeterminedperiod of time (e.g., 10 seconds). Upon elapse of the interimpredetermined period of time, the controller 58 concludes the firstcleaning mode, advancing the first fan 30 in sequence through T6 and T7,after which it commands the first fan 30 to a variable forward speed(assuming no abort). It subsequently concludes the second cleaning mode,advancing the second fan 36 in sequence through T5, T6, and T7, afterwhich it commands the second fan 36 to a variable forward speed(assuming no abort).

Thus, the controller 58 may be configured to operate the first andsecond fans 30, 36 sequentially in the first cleaning mode, the interimcleaning mode, and the second cleaning mode during an exchanger-cleaningevent, with the first and second cleaning modes overlapping to providethe interim cleaning mode.

Referring to FIG. 8, a control routine 310 provides an alternativeembodiment to control routine 110. The control routine 310 alternatesbetween the cooling mode and a cleaning mode, and the cleaning mode maybe activated in any suitable manner such as by elapse of a predeterminedperiod of time (e.g., step 112) or by manual request (e.g., step 114),assuming one of the inhibit conditions is not present (e.g., step 116).In other words, the routine 310 will perform steps 112, 114, and 116before performing a cleaning mode.

The control routine 310 is different in that each exchanger-cleaningevent involves only one of the first and second cleaning modes such thatsuccessive exchanger-cleaning events alternate between the first andsecond cleaning modes. For example, the control routine 310 may advancefrom the cooling mode in step 316 to only the first cleaning mode instep 318 (does not include the second cleaning mode during thisexchanger-cleaning event). The routine 310 may then advance back to thecooling mode in step 320 and then to only the second cleaning mode instep 322 (does not include the first cleaning mode during thisexchanger-cleaning event). This pattern may continue, promoting fueleconomy since both cleaning modes are not activated during anexchanger-cleaning event.

In step 318, the controller 58 operates the first and second fans 30, 36in their cleaning and cooling directions, respectively, in a mannersimilar to what is discussed in connection with step 118-1 of FIG. 6. Instep 320, the controller 58 returns the first fan 30 to its coolingdirection to a variable forward speed based on cooling need. In step322, the controller 58 operates the first and second fans 30, 36 intheir cooling and cleaning directions, respectively, in a manner similarto what is discussed in connection with step 118-2 of FIG. 6. Theroutine 310 then advances back to step 316, in which the controller 58returns the second fan 36 to its cooling direction to a variable forwardspeed based on cooling need. The controller 58 may thus be configured toalternate successive exchanger-cleaning events between the firstcleaning mode and the second cleaning mode. In the event an abort of thereversal sequence of either fan 30, 36 is triggered in any of T1-T7, thecontroller 58 performs the abort sequence associated with the respectivetime period (discussed above in connection with routine 110 and fan 30)without reversing the other fan, thereby aborting the exchanger-cleaningevent altogether.

In the control routine 110, it is thought that, during each of the firstand second cleaning modes, about 86 percent of the debris in the enginecompartment 18 is removed from the engine compartment while about 10percent remains.

In the control routines discussed herein, during a cleaning mode, theforward fan (i.e., the fan operating in its forward direction) isoperated at a variable forward speed based on cooling needs.Alternatively, the controller 58 may operate the forward fan at itsmaximum calibrated operating speed.

Cooling is more efficient in the cooling mode than any of the cleaningmodes, but also takes place during the exchanger-cleaning event.

The cooling system 22 may be used with an articulated machine (e.g.,machine 10) or a non-articulated machine.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such illustration and description isto be considered as exemplary and not restrictive in character, it beingunderstood that illustrative embodiment(s) have been shown and describedand that all changes and modifications that come within the spirit ofthe disclosure are desired to be protected. It will be noted thatalternative embodiments of the present disclosure may not include all ofthe features described yet still benefit from at least some of theadvantages of such features. Those of ordinary skill in the art mayreadily devise their own implementations that incorporate one or more ofthe features of the present disclosure and fall within the spirit andscope of the present invention as defined by the appended claims.

What is claimed is:
 1. A cooling system for a machine, comprising: afirst cooling package comprising a first fan and at least one heatexchanger to cool at least one fluid associated with the machine, thefirst fan configured to rotate in a cooling direction and an oppositecleaning direction, a second cooling package comprising a second fan andat least one heat exchanger to cool at least one fluid associated withthe machine, the second fan configured to rotate in a cooling directionand an opposite cleaning direction, and a fan control system configuredto alternate the first and second fans between a first cleaning mode anda second cleaning mode, wherein, in the first cleaning mode the firstand second fans concurrently rotate respectively in their cleaning andcooling directions advancing air in a first flow direction from thefirst fan to the second fan past the at least one heat exchanger of eachof the first and second cooling packages, and, in the second cleaningmode the first and second fans concurrently rotate respectively in theircooling and cleaning directions advancing air in a second flow directionopposite the first flow direction from the second fan to the first fanpast the at least one heat exchanger of each of the first and secondcooling packages.
 2. The cooling system of claim 1, wherein the fancontrol system is configured to alternate successively the first andsecond fans between the first cleaning mode and the second cleaning modeduring an exchanger-cleaning event.
 3. The cooling system of claim 1,wherein in the first cleaning mode the fan control system is configuredto command operation of the first fan at at least a predeterminedreverse speed threshold for a predetermined period of time, and in thesecond cleaning mode the fan control system is configured to commandoperation of the second fan at at least the predetermined reverse speedthreshold for the predetermined period of time.
 4. The cooling system ofclaim 3, wherein in each of the first and second cleaning modes thepredetermined period of time is cumulative excluding time that therespective first or second fan spends below the predetermined reversespeed threshold.
 5. The cooling system of claim 3, wherein the fancontrol system is configured to abort reversal of the first fan uponoccurrence of an abort event, and is configured to begin reversal of thesecond fan when a speed of the first fan reaches a zero fan speed or atthe end of a predetermined period of abort time if the speed of thefirst fan is below a low-speed threshold.
 6. The cooling system of claim1, wherein the fan control system is configured to alternate successiveexchanger-cleaning events between the first cleaning mode and the secondcleaning mode.
 7. The cooling system of claim 1, wherein the fan controlsystem is configured to operate the first and second fans sequentiallyin the first cleaning mode, an interim cleaning mode, and the secondcleaning mode during an exchanger-cleaning event, and, in the interimcleaning mode, the first and second fans concurrently rotaterespectively in their cleaning directions.
 8. A machine comprising thecooling system of claim 1, wherein the first and second cooling packagesare positioned on laterally opposite sides of a fore-aft axis of themachine such that the first and second flow directions are laterallyopposite to one another.
 9. The machine of claim 8, wherein the at leastone heat exchanger of the first cooling package and the at least oneheat exchanger of the second cooling package are positioned laterallybetween the first and second fans.
 10. The machine of claim 9, whereinthe machine is a work vehicle.